Workers at Montreal's Palais des congrès had to clean paint off the windows of the convention centre after the building was defaced by anti-Plan Nord slogans.

Palais des congrès anti-Plan Nord protest

Two Montreal police officers escort a protester from the Palais des congrès on Dec. 8, 2014. A small protest was held outside of the convention centre in protest against the province's Plan Nord. (Jay Turnbull/CBC)

Paint was splashed and anti-Plan Nord posters were pasted to the windows of the Montreal convention centre overnight ahead of the Board of Trade's Strategic Forum on Natural Resources.

"Non Plan Mort" — or "No to Plan Death" — was also sprayed on the windows.

Plan Nord is the provincial government's plan to develop natural resources in Quebec's north.

4 arrests

The demonstration began before the 7:30 a.m. convening of the forum on natural resources.

Of the dozen or so protesters, four were detained by police.

Two of them, a 28-year-old man and a 19-year-old woman, face charges for disturbing the peace. 

Another two men, a 28-year-old and a 22-year-old face charges of armed assault.